Sedimentary Provenance Changes Constrain the Eocene Initial Uplift of the Central Pamir, NW Tibetan Plateau

Abstract

The Pamir Plateau region of the Northwestern Tibetan Plateau forms a prominent tectonic salient, separating the Tajik and Tarim basins. However, the topographic evolution of the Pamir Plateau remains elusive, despite the key role of this region played in the retreat of the Paratethys Ocean and in aridification across Central Asia. Therefore, the SW Tarim and Tajik basins are prime locations to decipher the geological history of the Pamir Plateau. Here, we present detrital zircon U/Pb and apatite fission-track (DAFT) ages from the Keliyang section of the SW Tarim Basin. DAFT ages show that sediments had three components during the Late Cretaceous and two components since the Oligocene. Detrital zircon U/Pb ages mainly cluster between 400 and 500 Ma during the Late Cretaceous, and coincide with ages of the Songpan-Ganzi and the West Kunlun Mountains. In contrast, detrital zircon U/Pb ages in the Eocene sediments are centered at around 200–300 Ma and 40–70 Ma, with a peak at ∼45 Ma, consistent with data from the Central Pamir and the West Kunlun Mountains. The ∼45 Ma peak in detrital zircon U/Pb ages since the Eocene indicates a new sedimentary source from the Central Pamir. Non-metric multi-dimensional scaling (MDS) analyses also show that the sedimentary source was closer to the Central Pamir after the Eocene, when compared to the Late Cretaceous. The result shows a clear Eocene provenance change in the Keliyang area. Moreover, this Eocene provenance shift has been detected in previous studies, in both the Tajik and Tarim basins, suggesting that the entire Central Pamir region likely experienced quasi-simultaneous abrupt uplift and paleo-geomorphological changes during the Eocene.

Northward Growth of the West Kunlun Mountains: Insight From the Age–Elevation Relationship of New Apatite Fission Track Data

“…Previous low-temperature thermochronological studies in the study region have shown that the Pamir-WK experienced three rapid exhumation events during the Cenozoic at ∼50-40, ∼25-16, and between ∼10 Ma and the present day (Robinson et al, 2004;Robinson et al, 2007;Amidon and Hynek, 2010;Sobel et al, 2011;Wang et al, 2011;Carrapa et al, 2014;Li et al, 2019). Other studies have shown that a provenance change or increase in sediment flux occurred at ∼40-30, ∼26, and ∼15 Ma (Jiang and Li, 2014;Tang et al, 2015;Blayney et al, 2016;Sun et al, 2016;Wang et al, 2019;Zhang et al, 2019;Sun et al, 2020;Sakuma et al, 2021;Wang et al, 2021). The Paleogene paleotopography in the WK may therefore represent an ancient land surface (Li et al, 2019).…”

“…The dominance of Cenozoic northward-directed paleocurrents in the SW Tarim Basin indicates that the basin sediments were mainly derived from its southern margin (Sobel, 1999;Bershaw et al, 2012;Cao et al, 2014;Zhang et al, 2019;. Interestingly, an ∼45 Ma peak in detrital zircon U/Pb ages is documented only in the central Pamir and first appears in Eocene strata in the SW Tarim and Tajik basins (Blayney et al, 2016;Sun et al, 2016;Wang et al, 2019;Zhang et al, 2019;Sun et al, 2020;Wang et al, 2021). Previous documents indicated that this magmatic activity represented the Late Eocene rapid uplift in the central Pamir region, based on late Eocene detrital apatite fission track ages and regional tectonic movements (Wang et al, 2019;Zhang et al, 2019;Wang et al, 2021).…”

“…Interestingly, an ∼45 Ma peak in detrital zircon U/Pb ages is documented only in the central Pamir and first appears in Eocene strata in the SW Tarim and Tajik basins (Blayney et al, 2016;Sun et al, 2016;Wang et al, 2019;Zhang et al, 2019;Sun et al, 2020;Wang et al, 2021). Previous documents indicated that this magmatic activity represented the Late Eocene rapid uplift in the central Pamir region, based on late Eocene detrital apatite fission track ages and regional tectonic movements (Wang et al, 2019;Zhang et al, 2019;Wang et al, 2021). Moreover, detrital zircons with an age peak of ∼45 Ma are absent in sedimentary rocks that formed at ∼26 Ma in the Oyitag and after ∼26.5 Ma in the Aertashi sections of the SW Tarim Basin (Figure 6; Blayney et al, 2016;Sun et al, 2016), indicating that the influx of sediments from the central Pamir region was hindered by the growth of the mountains to the northern side of the basin.…”

“…As the sedimentary provenance in the SW Tarim and Tajik basins did not change between the Late Cretaceous and the Early Eocene, the topography of the nearby ranges must also not have changed during this time. The first quasi-synchronous rapid uplift of the central Pamir region occurred in the Late Eocene (40-30 Ma), and provided a new sediment flux into the SW Tarim and Tajik basins (Blayney et al, 2016;Wang et al, 2019;Zhang et al, 2019;Sun et al, 2020;Wang et al, 2021), although this occurred at the earliest time of ∼47 Ma in the Oytag section of the Tarim Basin (Sun et al, 2016). The second regional-scale rapid uplift in the SWK (this study) and northern Pamir region (Amidon and Hynek, 2010) occurred during the Oligocene; this lasted at least ∼9 Ma (from 25 to 16 Ma) in the northern Pamir region, but there are no geochronological data to constrain its duration in the SWK.…”

Mesozoic–Cenozoic multistage tectonic evolution of the Pamir: Detrital fission‐track constraints from the Tajik Basin

“…Detrital fission-track data have also been reported from the southwestern Tarim Basin (e.g. Cao et al, 2015;Clift et al, 2017;Wang et al, 2021). We did not incorporate these data in the compilation because a significant component of the detritus in these Tarim sections was sourced from the West Kunlun to the south, thus yielding information that may not be directly relevant to the Pamir.…”